If you are looking for a low cpu usage SSID logger written in C for the GNU/Linux platform, you just found one named ssid-logger.

ssid-logger was mainly created to log SSIDs and export the collected data to Wigle.net. It is able to run on a rpi0 for example, without requiring 100% cpu usage.

You will need a wifi card that is able to run in monitor mode and a GPS device recognized by gpsd.

ssid-logger uses the pcap library to listen passively for beacon management frames broadcasted by wifi access points, using a wifi card in monitor mode. It parses each beacon to extract the minimum data required to export to wigle.net. It logs each beacon AP alongside its GPS coordinates, acquired via the gpsd daemon. It automatically hops between 802.11n channels, at the default rate of 3 per second.

It can log to a sqlite3 database (by default) or to a csv file.

This is an all-in-one solution to log SSIDs. Even though kismet is a great software; it's wardrive mode might not be light enough for a rpi0 (may be a rpi0 v2 ?)

Note: ssid-logger does not automatically export the collected data to wigle.net. You will have to do it manually, if you want to (there is a helper script in ./scripts).

You run ssid-logger with:

$ sudo ssid-logger -i wlan0mon

where wlan0mon is a wifi interface already put in monitor mode.

The default output format is a sqlite3 database, named beacon.db. You can choose another name by using the -o switch. You can select to choose the csv format by using -f csv.

The complete usage:

Usage: ssid-logger -i IFACE [-f csv|sqlite3] [-o FILENAME] [-V] [-z] [-z]
  -i IFACE        interface to use
  -f csv|sqlite3  output format to use (default sqlite3)
  -o FILENAME     explicitly set the output filename
  -V              print version and exit
  -z              log ssid even if no gps coordinates are available
  -zz or -z -z    don't use gpsd and log all ssids

ssid-logger depends on the following libraries:

• libpcap
• libpthread
• libnl and libnl-genl
• libgps
• libsqlite3
• libwifi (if not found will be built as a subproject)

You also need gpsd up and running.

On Ubuntu 21.10 and later or Raspberry Pi OS, one needs to run the following command to install libraries and headers:

$ sudo apt install pkg-config libpcap0.8 libpcap0.8-dev libnl-3-200 libnl-3-dev libnl-genl-3-200 libnl-genl-3-dev gpsd libgps28 libgps-dev libsqlite3-dev libsqlite3-0 meson ninja-build

On archlinux-arm, this is (libnl is already installed):

$ sudo pacman -S libpcap gpsd sqlite3 meson ninja

To build the executable, you need meson and ninja.

$ cd ssid-logger
$ meson build
$ ninja -C build

• sqlite3_to_csv.py will allow to convert a sqlite3 .db file to a .csv one, if you change your mind afterwards and wants a csv file instead of a sqlite3 db.
• convert.py will allow you to get a GPS trace in GPX or KML format to visualize on a map your path, and the SSIDs encoutered. This will allow you to check your GPS device and see if it works OK.
• upload_to_wiglenet.sh helps you to upload the collected data to wigle.net via cli
• transactions.sh allows you to see your latest transactions/uploads on wigle.net